Radial piston-type hydraulic pump



Jan. 4, 1955 J. c. COTNER ET AL 2,698,585

RADIAL PISTON-TYPE HYDRAULIC PUMP Filed D60. 15, 1950 4 Sheets-Sheet lINVENTORS Wrren R. er

Jbizn L. 601 ner BY M ATTORNEY J. C. COTNER ET AL RADIAL PISTON-TYPEHYDRAULIC PUMP Jan. 4, 1955 4 Sheets-Sheet 2 Filed Dec. 15, 1950INVENTORS V Zv'r'en J2. Tuckcr John 6? Gathe BY 7W ATTORNEY m u E Jan.4, 1955 J. c. COTNER -T L 2,698,585

RADIAL PISTON-TYPE. HYDRAULIC PUMP Filed Dec. 15, 1950 4 Sheets-Sheet 5INVENTOR %7'762 3. 540i? FIGS- ATTORNEY Jan. 4, 1955 J. c. COTNER ETAL2,698,585

RADIAL PISTON-TYPE HYDRAULIC PUMP Filed D80. 15, 1950 4 Sheets-Sheet 4INVENTORS U] Warren E. Tuci'er' John C. dolner BY Wd KW ATTORNEY UnitedStates Patent M RADIAL PISTON-TYPE HYDRAULIC PUMP John C. Cotner andWarren R. Tucker, Mount Gilead, Ohio, assi nors to H-P-M DevelopmentCorporation, Mount Gilead, Ohio, a corporation of Delaware ApplicationDecember 15, 1950, Serial No. 201,018

3 Claims. (Cl. 103-161) The present invention relates generally tohydraulic pumps and/or motors, and has particular reference to animproved radial piston-type hydraulic pump or motor which ischaracterized by a structurally simple and rugged construction, andwhich incorporates an improved and mechanically eflicient connecting rodstructure between the pumping pistons and the eccentrically movablerotor member of the pump.

In the past, the ordinary type of radial piston hydraulic pumpcomprised, among other elements, a primary shaftdriven rotor formed witha plurality of radially disposed cylinders, a like number of pumpingpistons reciprocable in the cylinders, and an outer or secondary rotorto which one end of the pumping pistons was slidably connected, in orderthat the secondary rotor might be rotated in unison with the primaryrotor, while at the same time providing for shifting movement of thesecondary rotor to positions of eccentricity with respect to the primaryrotor to impart a pumping reciprocating action to the pistons. Inpreviously known constructions of this type, connection between theprimary and secondary rotors was accomplished solely through the pumpingpistons which were slidably connected with the secondary rotor to permitrelative shifting of the rotor with respect to the primary rotor toobtain a pumping action within the cylinders. The sliding connectionbetween the pumping pistons and the secondary rotor necessarilyincreased the amount of wear within the moving elements of the pump andin many cases resulted in a binding of the outer rotor in its shiftingmovement with respect to the primary rotor with consequent operatingdifliculties in varying the displacement of the pump. Further, due tothe sliding connection between the primary and secondary rotors, arelatively large number of parts were necessary to accomplish thedesired movement of the secondary rotor in varying the fluid output ofthe pump, and extremely accurate machining of the relatively movableparts was necessary to prevent undesired excessive friction and bindingof the relatively movable parts. Also, in the ordinary type of radialpiston pump, there is generally provided a stationary valve spindlehaving passages arranged to communicate with the separate cylinders ofthe primary rotor during relative rotation of such rotor about thestationary spindle. This feature of the pump further presents mechanicaldifficulties and greatly increases the cost of the pump due to theaccurate machining necessary to accomplish the desired relative rotationbetween the stationary spindle and the primary rotor, and obviously,such relative rotation increases the friction produced in the operationof the pump and the normal wear of the parts thereof.

It follows, therefore, that the primary object of the present inventionis to provide an improved radial pistontype pump which entirelyeliminates a sliding connection between the reciprocating piston membersand the secondary rotor of the pump, and which provides for thesimultaneous unified rotation of the primary and secondary rotors andthe valving structure associated with the pressure chambers or cylindersof the pump, thereby to greatly reduce the number of relatively movableelements within the pump structure, and consequent wear to the partsthereof.

It is another object of this invention to provide a radial piston-typepump or motor which comprises a primary shaft-driven rotor in which, isformed a plurallty of radially disposed pumping cylinders communicatingat 2,698,585 Patented Jan. 4, 1955 one end with separate fluid passagesextending in planes parallel to the axis of the rotor and in alignmentwith relatively stationary separate fluid inlet and outlet ports formedin the casing of the pump, a secondary rotor arranged for movementbetween concentric and eccentric positions relative to the primaryrotor, a plurality of rodconnected pumping pistons reciprocable in thecylinders of the primary rotor and pivotally connected with thesecondary rotor, and a free floating compensator ring disposed inlaterally offset relation to the rotors and connecting the primary andsecondary rotors for unified rotation, while at the same time providingfor shifting movement of the secondary rotor between concentric andeccentric positions relative to the primary rotor to thus provide forreciprocation of the pumping pistons within the pressure cylinders ofthe primary rotor and the consequent variable displacement of fluidbetween the inlet and outlet ports of the pump.

Yet another object of the invention is to provide, as a sub-combinationwithin a radial piston-type pump, a floating ring and connecting rodassembly between the primary and secondary rotors of the pump providingfor the simultaneous unified rotation of the primary and secondaryrotors while permitting shifting movement of the secondary rotor tovarious positions providing variable and reversible discharge ofpressure fluid from the pump.

For a further and more detailed understanding of the present inventionand the various additional objects and advantages realized therefrom,reference is made to the following description and the accompanyingdrawings, wherein:

Fig. l is a medial longitudinal vertical sectional view taken through ahydraulic pump formed in accordance with the present invention;

Fig. 2 is a transverse vertical sectional view taken along the line 2-2of Fig. l;

3 is a similar view taken along the line 3-3 of 1g.

Figs. 4-7 are diagrammatic views showing the various positions taken bythe compensator ring of the present pump as the same rotates when thepump is conditioned for displacement of fluid in one direction;

Fig. 8 is a transverse vertical sectional view taken along the line 88of Fig. l and showing the relation between the inlet and outlet ports ofthe pump casing and the respective fluid passages leading from thepumping cylinders of the pump.

Referring now to the drawings, the present pump comprises an outersectional casing consisting of a substantially rectangular central framesection 10 and opposite end sections 12 and 14 which are suitablyrigidly joined with the central frame section 10 in any suitable manner,such as by bolts, not shown, which pass transversely through the endsections and the central frame. The end sections and central frame areformed to provide an internal chamber 16 which houses the elements ofthe pumping mechanism to be hereinafter more fully described. At oneend, the end section 14 is provided with a reduced hub portion 18 inwhich is formed a pair of oppositely disposed fluid inlet-outlet ports20. Each of the ports 20 terminates at its inner end in an arcuatemanifold chamber 22 which opens into an axially disposed bore 24extending through the hub portion 18. Positioned within the bore 24 ofthe hub portion 18 is an annular valving member 26 which is formed witha pair of radially disposed arcuate manifold ports 28 in registrationwith the arcuate manifold chambers of the inlet-outlet ports 20. Each ofthe arcuate ports 28 of the valving member 26 terminates at its innerend in a relatively reduced perpendicularly extending arcuate passage 30which opens at one end of the valve member 26 inwardly of the pumpcasing. Advantageously, the valving member 26 is provided with packingrings 32 at its periphery to provide a fluid-tight fit between thevalving member 26 and the inner walls of the hub section 18 defining thebore 24. Adjoining the relatively enlarged bore 24 of the hub section 18is a reduced diameter bore 34 formed with a shouldered region 36 anddefining a chamber for the reception of a pair of anti-friction ballbearings 38. The bore 34 is closed at its outer end by an end cap 40which is SCUI 1 to the outer face of the hub section 18 as by cap screws42. The end cap is formed with an axial shaft-receiving opening 44through which extends a drive shaft 46. The shaft 46 is rotatablycarried within the inner races of the ball bearings 38, and mayadvantageously be formed with a diametrically enlarged shoulder region48 which functions to maintain a separation between the separate ballbearings 38. The shaft extends inwardly of the casing through an axialbore 50 'formed in the valve member 26, and terminates centrally of thepump casing in a splined outer end portion 52. The splined portion 52 ofthe shaft 46 is received within a cooperatively splined bore 54extending axially through an annular primary rotor 56.

As shown particularly in Fig. l of the drawings, the shaft 46 terminatesintermediate the ends of the bore 54 of the primary rotor 56, and asecond shaft 58 extends into the bore 54 from the opposite end thereofto abut the inner end of the shaft 46. The outer end of the second shaft58 extends through a bushing block 60 positioned within a recess 62formed upon the inner side wall of the casing section 12. The extremeouter end of the second shaft 58 is relatively diametrically enlargedand rotatably extends within a bore 64 formed axially through the endcasing section 12. Advantageously, the bore 64 of the end section 12 iscovered by a removable face plate 66 to provide access to the end of theshaft 58 to enable the same to be removed upon disassembly of the pump.

The primary rotor 56 is supported within the casing by anti-frictionbearings 68 which, in turn, are supported within annular recesses 69formed in the inner side Walls of the end sections 12 and 14. Theintermediate portion of the primary rotor 56 is relatively diametricallyenlarged with respect to the end hub portions thereof and is formed witha plurality of spaced radially disposed pumping cylinders or bores 70.Each of the cylinders 70 opens along the periphery of the rotor 56 andcommunicates at its inner end with separate fluid passages 72 extendinglongitudinally through the primary rotor 56 parallel to the axis thereofand terminating in the plane of the arcuate passages 30 formed in thevalving member 26. The primary rotor 56 is formed at the juncture of thecylinders 70 and passages 72 with relatively enlarged recesses 74opening into the passages 72 and providing for the unrestricted flow ofpressure fluid from the cylinders to the passages 72.

It will be understood that the primary rotor 56 is carried in rotationwith the drive shaft 46, and that upon rotation, the separate passages72 are sequentially brought into registration with the separate arcuatepassages 30 formed in the valving member 26, whereby fluid may betransfcrred from and to each of the passages 72 by way of the arcuatepassages or ports 20 of the valving member which, in turn, communicatewith the separate inlet-outlet ports 20 of the pump.

Extending within each of the cylinders 70 of the primary rotor is apumping piston 76 which is formed on its inner end with a piston headand which includes a hollow cylindrical skirt region openingunrestrictedly at its opposite end. Positioned within the skirt regionof each piston 76 is a bearing block 78 which is formed with asemispherical recess for the partial reception of the spherical headportion 80 of a connecting rod 82. The head portion 80 of each rod isretained within the piston by means of an annular split-ring collar 84which is provided with a semispherical recess engagcable with theopposite side of the spherical head 80 of the connecting rod 82. Thecollar 84 is abutted by a coil compression spring 86 which has itsopposite end retained within the piston by a split-ring retaining collar88 carried within an inner circular recess formed in the skirt portionof the piston 76. The block 78 and collar 84 provide a pivotal supportbetween the spherical head 80 of the connecting rod and the piston 76and permit limited swinging movement of the connecting rod within theskirt portion of the piston. The opposite end of each of the connectingrods 82 terminates in a relatively enlarged cylindrical boss region 90which is formed with an axial bore 92 for the reception of a wrist pin94. The wrist pin 94 extends outwardly on either side of the connectingrod and is nonrotatively carried within the bore 92 of the connectingrod by means of a set screw 96. The outer end portions of the wrist pin94 extend within axially aligned and opposed roller bearings 98 whichare positioned within bearing-receiving openings 100 formed in anannular secondary rotor 102.

The secondary rotor 102, in the regions of the connecting rods 82, isformed with radially disposed channeled recesses 104 which receive thecircular boss regions 90 of the connecting rods. The opposing walls ofthe recesses 104 are formed with the bores 100 which receive thebearings 98 and support the wrist pins 94 therebetween. The outerperipheral surface of the annular secondary rotor 102 slidably abuts theinner side surface of a circular ring 106 whose outer surface rides upona multiplicity of roller bearings 108 interposed between the outersurface of the ring 106 and the circular inner surface of a rectangularflow-controlling block 110. The flow-controlling block 110 is mountedwithin the outer casing for limited longitudinal shifting movement andhas its upper and lower surfaces slidably supported by a plurality ofwear plates or blocks 112 carried upon the inner side surface of thecentral casing frame 10 in substantially the corner regions thereof. Ateither end, the flow-controlling member 110 is provided with outwardlyextending control shafts or rods 114 extending through openings formedin the central casing frame 10. The control rods 114, in the usualmanner, may be mounted within a servomotor control of any suitable type,not shown, which functions to impart shifting movement to the block 110through the rods 114.

Rigidly bolted to one side of the secondary rotor, as at 115, is a ring116 which is formed with a pair of diametrically opposed bores 117 inwhich are carried a pair of radially extending rods 118. The rods 118are suitably secured within the bores of the ring 116 by means of setscrews 120 and are arranged to have their inner end portions extendthrough a pair of radially disposed and diametrically opposed bores 121formed in a circular and annular compensator ring 122. The ring 122 ispositioned in laterally offset relation to the primary and secondaryrotors and is carried in spaced relation to the diametrically enlargedintermediate region of the primary rotor. The ring 122 is formed in 90relation to the bores 121, which receive the rods 118, with a second setof bores 124 which slidably receive a second pair of radially disposedrods or posts 126 which, at their inner ends, are rigidly connected withthe relatively reduced hub portion of the primary rotor 56. Withreference to Fig. 3, it will be seen that the rods 118, which arecarried by the ring 116, occupy relatively diametrically opposedpositions in 90 relation to each of the rods 126 carried by the primaryrotor 56. This assembly, comprising the ring 122 and rods 118 and 126,permits limited shifting movement of the flow-controlling block 110 andof the secondary rotor 102 between concentric and eccentric positionswith respect to the primary rotor and the drive shaft 46. As the rods118 which are carried by the secondary rotor are shifted in eitherdirection laterally with respect to the primary rotor, the compensatorring 122 likewise shifts and slides relative to the rods 126 carried bythe primary rotor. At the same time, the rods 126 rotate with theprimary rotor, thus transmitting direct rotation to the ring 122,through the rods 118, and thence to the secondary rotor. In this manner,there exists a unified rotation between the primary and secondary rotorsof the pump, yet the secondary rotor is permitted to move relative tothe primary rotor to an eccentric position-on either side of the primaryrotor to cause relative reciprocation of the pistons 76 within thepumping chambers of the primary rotor and the consequent displacement offluid between the separate inlet-outlet ports 20 of the pump. The outerring 116 is slotted, as at 128, on either side of the rods 126 to permitthe ring 116 to be moved radially and eccentrically with respect to theprimary IOl6Ol without interference by the outer ends of the rods 12Fig. 3 of the drawings illustrates the various elements of the pump intheir neutral positions, wherein the primary and secondary rotors areconcentric to one another to prevent the reciprocation of the pistonsduring rotation of the rotors. In this neutral position, there is nocirculation of fluid between the separate ports 20 of the pump.

Figs. 4-7 illustrate the flow-controlling block 110 in a positionproviding for full displacement of fluid between the separate inlet andoutlet ports of the pump. The separate figures show the relativepositions of the free floating compensator ring 122 as the rotors aredriven in rotation with the flow-controlling block 110 shifted to itsfull left hand position. It will be seen from these latter figures thatthe compensator ring is rotated in unison with the rotors of the pump,but at the same time the axis of the compensator ring moves in acircular path relatlve to the axis of the primary rotor and drive shaft46, thus permitting free shifting movement of the flowcontrolling block110 and the secondary rotor 102 during rotation of the rotors of thepump.

Advantageously, the central frame of the casing may be formed along itslower sides to provide laterally and downwardly projecting base legportions 130 by which the pump casing may be suitably rigidly anchoredto a supporting structure. Further, the central frame section '10 may beformed upon its upper surface with an access opening 132 through whichlubricants may be introduced to the interior of the casing to lubricatethe sliding block or flow-controlling member 110. Also, for lubricatingpurposes, the end faces of the pistons 76 may be provided withrelatively small orifices or passages 134 through which hydraulic fluidmay pass from the passages 72 to lubricate the pivotal connectionbetween the spherical heads 80 of the connecting rods and the associatedbear ing surfaces of the blocks and collars 78 and 84.

Bolted on the side of the secondary rotor 102 opposite the ring 116 is asecond retaining ring 136 which overlaps the left hand end of the wristpins 94, as viewed in Fig. l, to maintain such wrist pins against unduelongitudinal shifting movement within the bearings 98, and thereby tomaintain the cylindrical boss regions 90 of the connecting rods inspaced relation to the inner side surfaces of the bearings 98 andprevent end wear thereto.

In operation, the mechanism constitutes a variable displacementreversible hydraulic pump, the secondary rotor being movable to eitherside of a concentric position relative to the primary rotor to reversethe direction of flow of fluid between the separate inlet and outletports of the pump. The rate of displacement of fluid between such portsis controlled by the extent of movement of the second rotoreccentrically of the primary rotor.

Assuming the drive shaft 46 to be drivingly connected with a suitablepower source, such as an electric motor, not shown, the shaft, primaryand secondary rotors, and the compensator ring 122 are rotated inunison. With the flow-controlling block 110 occupying its neutralposition as shown in Figs. 2 and 3, there is no transfer of fluidbetween the separate ports 20 of the casing due to the concentricdisposition of the primary and secondary rotors and the consequentimmobility of the pumping pistons within the pressure cylinders of theprimary rotor. However, when a discharge of pressure fluid through theupper inlet-outlet port 20 is desired, the flow-controlling block 110 isshifted leftwardly to its full line shown in Figs. 4-7. Such shiftingmovement imme diately moves the secondary rotor 102 to its maximum lefthand position of eccentricity with respect to the primary rotor 56, andas the rotors continue to rotate in unison, the pistons 76 are caused toing cylinders of the primary rotor to draw fluid into each of thecylinders through the lower inlet-outlet port 20 of the casing, thelower arcuate port of the valving member 26, and through thelongitudinal passages 72 as the latter are brought into registrationwith the lower arcuate port 30 during rotation of the primary rotor. Asthe primary rotor continues to rotate, each of the pistons 76, in itsturn, moves inwardly of its associated cylinder to force fluid withinthe cylinder outwardly throu h the passages 72 and the upper inet-outlet port 20 of the casing as the individual passages 72 arebrought into registration with the upper arcuate port 30 of the valvingmember 26. As shown in Fig. 8 of the drawings, the ends of the separatearcuate ports or passages 30 of the valving member 26 are disposed inrelatively closely spaced relation to minimize any tendency to compressfluid within the individual cylinders or to create a vacuum therein asthe passages 72 are closed ofl by the area of the valving member 26during rotation of the primary rotor relative thereto. Thus, the arcuateports 30 of the valving member are arranged to register with each of thepassages 72 associated with the individual cylinders 70 in a manner topermit flow of fluid to and from the passages during actual movement ofthe pistons within the cylinders and to close the passages 72 as thepistons reach top and bottom dead center positions. The degree ofshifting movement of the flow-controlling block 110 controls the lengthof stroke of each piston, and by increasing the eccentricity of thesecondary rotor with respect to the primary rotor, the strokes of themdivrdual position as reciprocate within the pump- 2 pistons arecorrespondingly increased with the result that the volume output of thepump is also increased,

The discharge of the pump is reversed in the usual manner by reversingthe position of the flow-controlling block 110, and it will beunderstood that by shifting the flow-controlling block rightwardly, asviewed in Figs. 27, a reversal of the direction of flow of fluid wouldresult, the upper inlet-outlet port 20 serving to supply fluid to thepump, while the lower inlet-outlet port 20 of the casing functions asthe pressure outlet of the urn p In view of the foregoing, it will beseen that the present invention provides an improved and mechanicallyeflicient radial piston-type hydraulic pump or motor which ischaracterized by its simplicity of construction and the employment ofrelatively few and simple movable parts. The provision of the novel freefloating compensator ring as a means for joining the separate primaryand secondary rotors of the pump for unified rotation greatly reducesthe amount of friction and wear in comparison with previous types ofradical piston pumps, and enables the individual pumping pistons to bemounted upon relatively simple connecting rod and wrist pin assemblies.Further, the generally rectangular outer configuration of theflow-controlling member of the present pump and the cooperativefour-corner support of the flow-controlling member within the outercasing greatly reduces the amount of wear between the sliding surfacesof such members and effectively resists any tendency of theflow-controlling member to cock due to torque forces transmitted uponrotation of the rotors of the pump. A further advantage ambient to thepresent pump construction stems from the provision of the valving member26 of the pump which remains stationary with respect to the rotatingprimary rotor and its associated fluid passages 72. In utilizing thestationary valving member 26, the ordinary valve spindle, which usuallyrotatively supports the primary rotor of the pump, is eliminated in itsentirety, thereby enabling the primary rotor to be directly keyed orsplined to an axially disposed drive shaft, thereby eliminating thenecessity for an axially offset connection between the drive shaft andthe primary rotor of the pump.

While a single preferred embodiment of the present invention has beendisclosed in detail, it will be understood that various modificationsrespecting constructional details may be resorted to without departingfrom the spirit of the invention or the scope of the following claims.

We claim:

1. In a fluid displacement pump: in combination, a casing formed with aninternal chamber, a fluid inlet, and a fluid outlet; a circular primaryrotor journaled for axial rotation within the chamber of said casing,said primary rotor being formed with a plurality of radially disposedpumping cylinders and a plurality of fluid-conducting passages disposedin parallel but radially oflset relation to the axis of said primaryrotor, each of the passages of said primary rotor communicating with oneof the pumping cylinders formed in said primary rotor and being arrangedfor alternate communication with the fluid inlet and outlet of saidcasing upon rotation of said primary rotor; a drive shaft extending intosaid casing and drivingly connected with said primary rotor; a secondaryrotor positioned in the chamber of said casing around said primaryrotor; piston means carried by said secondary rotor and reciprocable inthe pumping cylinders of said primary rotor; a first set ofdiametrically opposed radially and outwardly extending rods carried bysaid primary rotor; a second set of diametrically opposed radially andinwardly extending rods carried by said secondary rotor in right angularrelation to said first set of rods; a ring having diametrically opposedsets of openings slidably receiving said first and second sets of rodsand thereby joining said primary and secondary rotors for unifiedrotational movement while permitting movement of said secondary rotorbetween concentric and eccentric posi tions relative to said primaryrotor, the movement of said secondary rotor to positions of eccentricitywith respect to said primary rotor providing for reciprocation of saidpiston means within the cylinder of said primary rotor and thedisplacement of fluid between the inlet and outlet of said casing; andmeans in the chamber of said casing engaging said secondary rotor formoving the latter between concentric and eccentric positions withrespect to said primary rotor.

2. In a fluid displacement apparatus: a casing having an internalChamber fl T smarter: seats; at as; r axia rotation, said primary rotorb a plurality of radially a'ran d eing formed w th ducting P ges communicat i? cy-mder-s h said lmd d extending longitudinally i Witd y ers analternate communi ation with th l; Primary rotor r d mlet and [1 meansof said casing upon IOIZIIOI I of d Du et a piston reciprocable in eachof t Sai pnmary rotof; Sald ne cylinders formed in marriaes;astreamers:arte s relation to the outer perimeter of said prim ary rggl ifi e lng rods pivotally connected at one end with each of sald Rmeans pivotally connecting said rods at their opposite ends wlth saidsecondary rotor; flow-controlling means surrounding said secondary rotorand movable Within said casing to shift said secondary rotor betweenconcentric and eccentric positions with respect to the axis of saidprimary rotor; and means independent of said connecting rods unitingsaid primary and secondary rotors for rotation and permitting shiftingmovement of said secondary rotor during rotation thereof betweenconcentric and eccentric positions relative to said primary rotor tocause reciprocation of said pistons within the cylinders of said primaryrotor and the displacement of fluid between the inlet and outlet meansof said casing, said lastnamed means comprising a plurality of radiallyand outwardly extending rods carried by said primary rotor, a pluralityof radially and inwardly extending rods carried on said secondary rotor,and a floating ring member having radially disposed openings slidablyreceiving said rods. 3. In hydraulic fluid displacement apparatus: acasing formed with an internal rotor-receiving chamber, a fluid inletport, a fluid outlet port, and passage means connecting the inlet andoutlet ports with the rotor-receiving chamber; shaft means journaled insaid casing and extending axially through the rotor-receiving chamberthereof; a first primary rotor positioned in the chamber of said casingand drivingly connected with said shaft means, said primary rotor beingformed with a plurality of radially arranged and relatively spacedpumping chambers opening inwardly from said primary rotor and aplurality of se ar said prima i ii 523 22 3 exhendlng qngltudmally ofchambers formed therein t l i e c l i iiiigls g Pumping rotor beingarranged fofzlte t P ry the Passage means of said casin a ecommum-catlon and outlet ports u on g assqclatefi with the Inlet annularsecondary iotoi g i n e i r l ih t r ii zfme l fi g casing around saidprimary rotor and m b a] concentric and eccentric positions with 22 1ebetweqn nmar pect to said {it the gu iifiiii iif r s i iii iiifii i f mgQds pivotally connected at one end ti' ler e f vv fli li of SaldPlstons; means Pivotally connecting the g t ends of said rods with saidsecondary rotorfio z -cizt n trolling means slidable within the chamberof said casing and engageable with said secondary rotor for moving thelatter between concentric and eccentric positions With respect to saidprimary rotor; and means other than said connecting rods positionedwithin the chamber of said casing and drivingly connecting said primaryand secondary rotors for unified rotation but providing for movement ofsaid secondary rotor between concentric and eccentric positions withrespect to said primary rotor during rotation of said rotors, saidlast-named means comprising a pair of diametrically opposed rods carriedby and projecting radially outwardly on one side of said primary rotor,a second pair of diametrically opposed rods carried by and projectingradially inwardly on one side of said secondary rotor, and a floatingring having a plurality of radially arranged openings slidably receivingsaid first and second pairs of rods.

References Cited in the file of this patent UNITED STATES PATENTS697,019 Richardson Apr. 8, 1902 2,173,432 Benedek Sept. 19, 19392,273,468 Ferris Feb. 17, 1942 2,381,741 Grosser Aug. 7, 1945 2,397,314Grosser Mar. 26, 1946 2,419,059 De Villiers Apr. 15, 1947

